Migrate all apps to defpage declarative page routes

Replace Python GET page handlers with declarative defpage definitions in .sx
files across all 8 apps (sx docs, orders, account, market, cart, federation,
events, blog). Each app now has sxc/pages/ with setup functions, layout
registrations, page helpers, and .sx defpage declarations.

Core infrastructure: add g I/O primitive, PageDef support for auth/layout/
data/content/filter/aside/menu slots, post_author auth level, and custom
layout registration. Remove ~1400 lines of render_*_page/render_*_oob
boilerplate. Update all endpoint references in routes, sx_components, and
templates to defpage_* naming.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

market/bp/all_markets/routes.py

@@ -2,70 +2,57 @@
 All-markets blueprint — shows markets across ALL pages.
 
 Mounted at / (root of market app). No slug context.
-
-Routes:
-  GET  /              — full page with first page of markets
-  GET  /all-markets   — HTMX fragment for infinite scroll
+GET / handled by defpage. GET /all-markets is pagination fragment.
 """
 from __future__ import annotations
 
-from quart import Blueprint, g, request, render_template, make_response
+from quart import Blueprint, g, request
 
-from shared.browser.app.utils.htmx import is_htmx_request
 from shared.sx.helpers import sx_response
 from shared.infrastructure.data_client import fetch_data
 from shared.contracts.dtos import PostDTO, dto_from_dict
 from shared.services.registry import services
 
 
+async def _load_markets(page, per_page=20):
+    """Load all markets + page info for container badges."""
+    markets, has_more = await services.market.list_marketplaces(
+        g.s, page=page, per_page=per_page,
+    )
+
+    # Batch-load page info for container_ids
+    page_info = {}
+    if markets:
+        post_ids = list({
+            m.container_id for m in markets
+            if m.container_type == "page"
+        })
+        if post_ids:
+            raw_posts = await fetch_data("blog", "posts-by-ids",
+                                         params={"ids": ",".join(str(i) for i in post_ids)},
+                                         required=False) or []
+            for raw_p in raw_posts:
+                p = dto_from_dict(PostDTO, raw_p)
+                page_info[p.id] = {"title": p.title, "slug": p.slug}
+
+    return markets, has_more, page_info
+
+
 def register() -> Blueprint:
     bp = Blueprint("all_markets", __name__)
 
-    async def _load_markets(page, per_page=20):
-        """Load all markets + page info for container badges."""
-        markets, has_more = await services.market.list_marketplaces(
-            g.s, page=page, per_page=per_page,
-        )
-
-        # Batch-load page info for container_ids
-        page_info = {}
-        if markets:
-            post_ids = list({
-                m.container_id for m in markets
-                if m.container_type == "page"
-            })
-            if post_ids:
-                raw_posts = await fetch_data("blog", "posts-by-ids",
-                                             params={"ids": ",".join(str(i) for i in post_ids)},
-                                             required=False) or []
-                for raw_p in raw_posts:
-                    p = dto_from_dict(PostDTO, raw_p)
-                    page_info[p.id] = {"title": p.title, "slug": p.slug}
-
-        return markets, has_more, page_info
-
-    @bp.get("/")
-    async def index():
+    @bp.before_request
+    async def _prepare_page_data():
+        """Load all-markets data for defpage routes."""
+        endpoint = request.endpoint or ""
+        if not endpoint.endswith("defpage_all_markets_index"):
+            return
         page = int(request.args.get("page", 1))
         markets, has_more, page_info = await _load_markets(page)
-
-        ctx = dict(
-            markets=markets,
-            has_more=has_more,
-            page_info=page_info,
-            page=page,
-        )
-
-        from shared.sx.page import get_template_context
-        from sx.sx_components import render_all_markets_page, render_all_markets_oob
-
-        tctx = await get_template_context()
-        if is_htmx_request():
-            sx_src = await render_all_markets_oob(tctx, markets, has_more, page_info, page)
-            return sx_response(sx_src)
-        else:
-            html = await render_all_markets_page(tctx, markets, has_more, page_info, page)
-            return await make_response(html, 200)
+        g.all_markets_data = {
+            "markets": markets, "has_more": has_more,
+            "page_info": page_info, "page": page,
+        }
 
     @bp.get("/all-markets")
     async def markets_fragment():